A comparison of the rate of bacterial contamination for prefilled disposable and reusable oxygen humidifiers

Background: Prefilled disposable oxygen humidifiers are considered to prevent nosocomial pneumonia in hospital wards. However, their usefulness in intensive care units (ICUs) has not yet been established. In this study, we evaluated and compared contamination in prefilled disposable oxygen humidifiers and that in reusable oxygen humidifiers. Methods: Six oxygen outlets in the ICU were used. Prefilled disposable oxygen humidifiers and reusable oxygen humidifiers were attached to each wall-mounted oxygen outlet using a 2-way connector. Nonsterile nasal cannulae and tubes were connected to the humidifiers through which 5 L/min of oxygen was delivered continuously. Water samples (5 mL) from each humidifier were collected on the first day and every 7 days thereafter for a period of 56 days. Each water sample was incubated aerobically at 35°C for 48 hours and observed daily for bacterial growth. Results: Bacterial growth was observed only once in one sample from each humidifier type. Gram-positive cocci, 40 colony-forming units in the disposable oxygen humidifier and 10 colony-forming units in the reusable oxygen humidifier, were detected. Dust was observed from the 35th day onward only in the reusable oxygen humidifier. Conclusion: In the ICU, bacterial contamination does not occur in oxygen humidifiers even after 56 days of continuous use. However, dust does accumulate in the reusable oxygen humidifier after 35 days of continuous use.